Noise reduction is the process of removing noise from a signal. All recording devices, both analog and digital, have traits which make them susceptible to noise. Noise can be random white noise with no coherence, or coherent noise introduced by the device's mechanism or processing algorithms. When recording or capturing a primary sound source, noise may also be introduced by background sources. These background sources may contribute to an ambient background noise level. The background noise level may typically be of a lesser intensity than the primary sound source; however, the background noise level may include large spikes of noise that significantly interfere with the primary sound source. Additionally, continuous background noise may reduce the quality of the captured or recorded sound from the primary sound source.
Mobile devices may introduce a particular operating environment that is uniquely susceptible to background noise. In many cases, mobile devices may be equipped with two microphones, and the comparison between the voice level recorded by each microphone may be used to remove noise from a recorded or captured voice signal.